This invention relates to the field of mechanical connectors, and in particular to connector assemblies for spacecraft stage separation systems, such as satellite and missile systems.
Transport systems, such as rockets that transport satellites into space, vessels that transport submerged sections of ocean structures such as oil platforms, and the like, require a means for securely fastening different items together for transport, and reliably and easily unfastening the items for deployment. Multi-stage rockets also require a means for fastening the stages together, and reliably unfastening the stages as each stage is spent.
A variety of devices have been developed to secure two items together while also allowing the items to be separated quickly and reliably. In the aerospace industry, traditional connection devices include bolts and bands that can be severed. Bolts are used to fasten the two items together, and an explosive charge is typically used to sever the bolts at the proper time, thereby unfastening the two items. Depending upon the application, supplemental devices such as springs may be used to urge the two items apart when the bolts are severed. To assure a reliable separation, the number of bolts used to fasten the two items is kept to a minimum; this results in load points at the bolts far in excess of the load imposed by a distributed fastening system.
Belt structures are commonly used to provide for a distributed load. A belt structure that is commonly employed to fasten items together is a “V-band”, typified by U.S. Pat. No. 4,715,565, incorporated by reference herein. The V-band includes a tension belt for securing a plurality of retainers against camming surfaces on flange members on separable spacecraft component parts. A typical V-band embodiment consists of an upper ring attached to the payload, a lower ring attached to the launch vehicle, and a clampband that is circumferentially tensioned to the flanges of the upper and lower rings. The clampband is conventionally tensioned by bolts, and explosive bolt cutters are used to sever the bolts to release the tension.
For V-bands to work properly, the tension required in the clampband is relatively high (about 3800 pounds for a 38 inch diameter; 6800 pounds for a 66 inch diameter), requiring radial stiffeners in the rings. The sudden release of this stored energy generates high shock, and imposes additional requirements on the means used to retain the fast moving clampband and clamps after separation. Because of the high tension requirements, the combined weight of the belt, clamps, and supplemental required devices is substantial (as much as 25 pounds for a 38 inch diameter V-band structure). The high tension requirements of V-bands often require specialized tools and instruments to tension the band. The high tension and high release shock effects also limit the reliable life of the components, thereby limiting the amount of testing that can be applied to the components that are actually flown.
Another structure that is commonly used to provide for an easily separable connection is an explosive frangible joint, as typified by U.S. Pat. Nos. 4,685,376 and 5,390,606. An explosive detonating cord is placed within a contained space that forms the frangible joint between the two items. Separation is achieved by detonating the cord within the contained space, forcing a rapid crack propagation through the frangible joint. Although the weight of an explosive frangible joint is less than that of an equivalent sized V-band, it is still substantial (as much as 17 pounds for a 38 inch diameter joint). The destructive nature of this separation system precludes testing of the joints that are actually flown.
In 1999, Planetary Systems Corporation introduced a spacecraft connection system (the “Lightband”) that is light weight, does not use explosives, does not impart a substantial shock to the connected items upon separation, and is non-destructive, allowing for repeated use during testing prior to launch.
As detailed in U.S. Pat. Nos. 6,227,493 and 6,343,770, each incorporated by reference herein, and as illustrated in FIGS. 1A and 1B, the Lightband comprises a first component 110 having a plurality of leaf elements 115 with protrusions, and a second component 120 having recesses 125 for receiving the leaf element protrusions. The protrusions of the leaf elements are secured within the recess by a retaining band, which may be a compressed band, or in an alternative embodiment, an expansion band; the protrusions and recess are formed so as to provide a load and torque bearing surface that requires minimal tension on the tensioned band, or minimal compression on the expansion band. Electric motors 150 are used to transition between a lock state and a release state, each state being mechanically stable (unstressed). When the band is released, springs 130 in the hinge of the leaves 115, or other means, urge the leaves 115 away from the mating surfaces 125, thereby allowing for the separation of the connected items. Springs 140 are also used to urge the second component 120 away from the first component 110. Preferably, the leaves 115 are hinged, allowing for ease of coupling and decoupling to the mating surface 125.
Although the Lightband eliminates the inherent danger of explosives during pre-launch assembly and testing, minimizes the shock effects during separation, and provides a connector component that is stiff, strong, and easy to use, it is fairly expensive to manufacture and assemble. An 8″ diameter Lightband, for example, may have as many as 11 leaf elements and hinges that are machined from 0.5″ aluminum stock, and the assembly procedure must conform to rigorous standards.
It would be advantageous to reduce the number and cost of parts used in a non-explosive connector assembly. It would also be advantageous to reduce the cost and complexity of the assembly process.
These advantages, and others, are achieved by creating an integral component that can be deformed and placed into a stable state that locks the component into a mating component, and can easily be released from the deformed state, decoupling the two components. The integral component may include a central ring, a plurality of leaf elements arranged at the perimeter of the component, and a plurality of fins that extend outward from the ring to the plurality of leaf elements. A rotation of the ring element while the component is held stationary causes the fins to urge the leaf elements toward the receiving surface areas and to subsequently tension the leaf elements against surfaces on the mating component. To reduce cost and complexity, the integral component is a metal, such as titanium, that can be formed using an additive manufacturing process, commonly termed a 3-D printing process.
Throughout the drawings, the same reference numerals indicate similar or corresponding features or functions. The drawings are included for illustrative purposes and are not intended to limit the scope of the invention.